Effect of Adsorbent Pretreatments on Methanol Content and Quality of Jujube Wine

Jujube wine production faces the technical challenge of excessive methanol formation due to the high pectin content of the raw material. This study systematically compared five pre-fermentation treatments (pectinase, chitosan, bentonite, gelatin, and diatomite) for their effects on the methanol content and overall quality of jujube wine, aiming to identify an adsorbent pretreatment strategy that effectively reduces methanol levels while preserving wine quality. Using pectinase treatment as a reference control (representing conventional industrial pectin degradation), the results showed that all adsorbent treatments reduced the pectin content in jujube juice, thereby influencing methanol generation in the fermented wine. Notably, chitosan pretreatment exhibited the most pronounced methanol reduction (113.35 mg/L), which was 59.20% lower than that of the pectinase reference group (277.65 mg/L), and remained far below the methanol limits stipulated by Chinese, EU, and OIV standards (≤400 mg/L). This effectiveness is attributed to the positively charged nature of chitosan, which efficiently removes negatively charged pectin through electrostatic adsorption, thereby blocking methanol formation at the source. Chitosan treatment also resulted in the highest alcohol content (5.82%) and significantly reduced organic acid levels but concurrently led to a slight decrease in some key aroma esters. However, sensory evaluation revealed that jujube wine produced from the chitosan-pretreated juice maintained a harmonious overall taste profile, with an overall score comparable to that of the pectinase reference group. In comparison, bentonite and gelatin showed moderate effectiveness, while diatomite performed poorly. Notably, although pectinase treatment yielded the lowest pectin content, it paradoxically resulted in the highest methanol levels, highlighting the critical mechanism of pectin degradation (rather than removal) promoting methanol formation. In conclusion, chitosan was recommended as an effective pre-fermentation treatment strategy for producing jujube wine with a significantly reduced methanol risk. This study provided a theoretical basis and technical reference for the safe, high-quality industrial production of jujube wine.